(a) Field of the Invention
The present invention relates to a rangefinder. More specifically, the present invention relates to a laser rangefinder and method thereof.
(b) Description of the Related Art
Conventional laser rangefinders generally use high-power lasers of several megawatts, and intensities of signals reflected from a target (target signals) are much higher than those of system noise including optical noise, detector noise, and amplifier noise, and accordingly, the laser rangefinders easily detect the target signals through a simple threshold detection method.
However, since the high-power lasers may damage human eyes, the laser outputs have recently been regulated, and a need for rangefinders that use low-power laser diodes that are safe for the eyes has been raised. Thus, new signal processing technology studies for increasing the ranges have actively progressed.
A representative laser diode rangefinder for eyesight protection is an electro-optical system for geodetic surveys, which is currently sold in the commercial market. However, since the electro-optical system shoots modulated laser beams toward a retroreflector installed on a target location, and detects a phase of the signal reflected from the retroreflector to find a range, it is far different from the electro-optical system that uses a pulse detection method without the retroreflector in the principle of signal processing techniques.
Since an output of the target signal reflected from the target is less than the system noise including optical noise, detector noise, and amplifier noise in the electro-optical system using low-power laser diodes and the pulse detection method, it is not easy to detect the target signal. Accordingly, signal processing techniques for accurately detecting a target signal in a rangefinder that uses low-power laser diodes for eyesight protection are required.